Regarding the thread subject, I guess voiding the bank transaction would result in negative balance on Petty Cash account in some  point of account history, so voiding is forbidden.
Janusz

I think your guessing is not correct, because my Petty Cash account was in negative balance, and lately I correct the balance to positive then I delete the transaction (which was in the negative history) with no errors.

Adel

I was trying to void the transaction through (Delivery Note)'s type and the message was appeared as:

But, after I play around I try to void it through (Sales Invoice)'s type and it's DONE!
both transactions had been deleted.

The problem was from me and the message:

which didn't lead me to the real mistake.

regards

Adel

function handle_void_transaction()
{
    if (check_valid_entries()==true) 
    {
        $void_entry = get_voided_entry($_POST['filterType'], $_POST['trans_no']);
        if ($void_entry != null) 
        {
            display_error(_("The selected transaction has already been voided."), true);
            unset($_POST['trans_no']);
            unset($_POST['memo_']);
            unset($_POST['date_']);
            set_focus('trans_no');
            return;
        }

        $ret = void_transaction($_POST['filterType'], $_POST['trans_no'],
            $_POST['date_'], $_POST['memo_']);

        if ($ret) 
        {
            display_notification_centered(_("Selected transaction has been voided."));
            unset($_POST['trans_no']);
            unset($_POST['memo_']);
            unset($_POST['date_']);
        }
        else {
            display_error(_("The entered transaction does not exist or cannot be voided."));
            set_focus('trans_no');

        }
    }
}

Shouldn't the second if condition have it's logic inverted?
The line above:

        if ($void_entry != null) 

will probably need to become

        if ($void_entry == null) 

This should actually mean that unless there are entries to be voided, do not attempt to void any (since none exist).

However, in @dedode's case, he must find out why a "missing" transaction was sought to be voided in the first place! Possibly attempting to void an already voided transaction - using the back button in the browser and re-submitting it or some browser cache issue.......

When I try to void a transaction I've shown this message:

I have two accounts:
1- 1065 Petty Cash
2- 1060 Checking Account

I am sure that their bank balance is positive not negative.

So what's wrong?

I've seen this info after I set $go_debug in config.php file to 2, while 1 didn't show any extra info!

regards